net: fix uninitialized variable issue

msg_iocb needs to be initialized on the recv/recvfrom path.
Otherwise afalg will wrongly interpret it as an async call.

Cc: stable@vger.kernel.org
Reported-by: NHarald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: NTadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/socket.c

@@ -1695,6 +1695,7 @@ SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, size_t, size,
 	msg.msg_name = addr ? (struct sockaddr *)&address : NULL;
 	/* We assume all kernel code knows the size of sockaddr_storage */
 	msg.msg_namelen = 0;
+	msg.msg_iocb = NULL;
 	if (sock->file->f_flags & O_NONBLOCK)
 		flags |= MSG_DONTWAIT;
 	err = sock_recvmsg(sock, &msg, iov_iter_count(&msg.msg_iter), flags);